The present invention involves the ejection of ink drops by way of forming gas or vapor bubbles in a bubble forming liquid. This principle is generally described in U.S. Pat. No. 3,747,120 (Stemme). Each pixel in the printed image is derived ink drops ejected from one or more ink nozzles. In recent years, inkjet printing has become increasing popular primarily due to its inexpensive and versatile nature. Many different aspects and techniques for inkjet printing are described in detail in the above cross referenced documents.
Clogging is one of the principle causes of nozzle failure. Nozzles can clog from dried ink and contaminants in the ink. However, gas bubbles entrained in the ink flow are also seriously detrimental to nozzle operation. The easily compressible gas absorbs the pressure pulse from the actuator and prevents droplet ejection.